From 35e48ca01808f1d21fe939b4bed964b6148286e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rafa=C5=82=20Krzywa=C5=BCnia?= <r.krzywaznia@gmail.com>
Date: Fri, 16 Jan 2026 02:30:55 +0100
Subject: [PATCH] feat(coding-agent): extension command argument autocomplete

---
 packages/coding-agent/CHANGELOG.md            |  1 +
 packages/coding-agent/docs/extensions.md      | 19 +++++++++++++++++++
 .../src/core/extensions/loader.ts             |  2 +-
 .../coding-agent/src/core/extensions/types.ts |  4 +++-
 .../src/modes/interactive/interactive-mode.ts |  1 +
 5 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index ec74ca4f..2b6743ed 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Added
 
 - Added bash-style argument slicing for prompt templates ([#770](https://github.com/badlogic/pi-mono/pull/770) by [@airtonix](https://github.com/airtonix))
+- Extension commands can provide argument auto-completions via `getArgumentCompletions` in `pi.registerCommand()` ([#775](https://github.com/badlogic/pi-mono/pull/775) by [@ribelo](https://github.com/ribelo))
 
 ### Fixed
 
diff --git a/packages/coding-agent/docs/extensions.md b/packages/coding-agent/docs/extensions.md
index 248d0c98..668de64e 100644
--- a/packages/coding-agent/docs/extensions.md
+++ b/packages/coding-agent/docs/extensions.md
@@ -882,6 +882,25 @@ pi.registerCommand("stats", {
 });
 ```
 
+Optional: add argument auto-completion for `/command ...`:
+
+```typescript
+import type { AutocompleteItem } from "@mariozechner/pi-tui";
+
+pi.registerCommand("deploy", {
+  description: "Deploy to an environment",
+  getArgumentCompletions: (prefix: string): AutocompleteItem[] | null => {
+    const envs = ["dev", "staging", "prod"];
+    const items = envs.map((e) => ({ value: e, label: e }));
+    const filtered = items.filter((i) => i.value.startsWith(prefix));
+    return filtered.length > 0 ? filtered : null;
+  },
+  handler: async (args, ctx) => {
+    ctx.ui.notify(`Deploying: ${args}`, "info");
+  },
+});
+```
+
 **Examples:** [custom-footer.ts](../examples/extensions/custom-footer.ts), [custom-header.ts](../examples/extensions/custom-header.ts), [handoff.ts](../examples/extensions/handoff.ts), [pirate.ts](../examples/extensions/pirate.ts), [plan-mode/index.ts](../examples/extensions/plan-mode/index.ts), [preset.ts](../examples/extensions/preset.ts), [qna.ts](../examples/extensions/qna.ts), [send-user-message.ts](../examples/extensions/send-user-message.ts), [snake.ts](../examples/extensions/snake.ts), [summarize.ts](../examples/extensions/summarize.ts), [todo.ts](../examples/extensions/todo.ts), [tools.ts](../examples/extensions/tools.ts)
 
 ### pi.registerMessageRenderer(customType, renderer)
diff --git a/packages/coding-agent/src/core/extensions/loader.ts b/packages/coding-agent/src/core/extensions/loader.ts
index d581b528..a6bcafda 100644
--- a/packages/coding-agent/src/core/extensions/loader.ts
+++ b/packages/coding-agent/src/core/extensions/loader.ts
@@ -150,7 +150,7 @@ function createExtensionAPI(
 			});
 		},
 
-		registerCommand(name: string, options: { description?: string; handler: RegisteredCommand["handler"] }): void {
+		registerCommand(name: string, options: Omit<RegisteredCommand, "name">): void {
 			extension.commands.set(name, { name, ...options });
 		},
 
diff --git a/packages/coding-agent/src/core/extensions/types.ts b/packages/coding-agent/src/core/extensions/types.ts
index e837cf40..0c2f656c 100644
--- a/packages/coding-agent/src/core/extensions/types.ts
+++ b/packages/coding-agent/src/core/extensions/types.ts
@@ -16,6 +16,7 @@ import type {
 } from "@mariozechner/pi-agent-core";
 import type { ImageContent, Model, TextContent, ToolResultMessage } from "@mariozechner/pi-ai";
 import type {
+	AutocompleteItem,
 	Component,
 	EditorComponent,
 	EditorTheme,
@@ -655,6 +656,7 @@ export type MessageRenderer<T = unknown> = (
 export interface RegisteredCommand {
 	name: string;
 	description?: string;
+	getArgumentCompletions?: (argumentPrefix: string) => AutocompleteItem[] | null;
 	handler: (args: string, ctx: ExtensionCommandContext) => Promise<void>;
 }
 
@@ -714,7 +716,7 @@ export interface ExtensionAPI {
 	// =========================================================================
 
 	/** Register a custom command. */
-	registerCommand(name: string, options: { description?: string; handler: RegisteredCommand["handler"] }): void;
+	registerCommand(name: string, options: Omit<RegisteredCommand, "name">): void;
 
 	/** Register a keyboard shortcut. */
 	registerShortcut(
diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
index 7677e116..4a4cdc5b 100644
--- a/packages/coding-agent/src/modes/interactive/interactive-mode.ts
+++ b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
@@ -319,6 +319,7 @@ export class InteractiveMode {
 			(cmd) => ({
 				name: cmd.name,
 				description: cmd.description ?? "(extension command)",
+				getArgumentCompletions: cmd.getArgumentCompletions,
 			}),
 		);